It is well known that a bed of molecular beads (constituting a molecular sieve) in a container will adsorb gases and odors from air forced through the container and the molecular sieve bed. The gases and odors are pulled down inside the minute pores of the molecular beads. The gas and odor molecules have a critical diameter rated from two to ten angstroms. By selecting an appropriate molecular sieve (for instance a three A, four A, five A, or ten A molecular sieve, or a mixture of such molecular sieves), different undesirable gases and odors can be adsorbed.
A problem arises when forcing air through a molecular sieve bed to remove gases and odors. This problem is based on the fact that the molecular beads of the bed also have an affinity for moisture. Moisture in the air being filtered will first collect on the surfaces of the beads, and will thereafter work its way into the bead pores. Moisture in the bead pores reduces the amount of gases and odors that can be drawn into the pores and therefore reduces the working life of the molecular sieve.
The present invention is based upon the discovery that, if a central passage is provided through the molecular sieve bed and its container, and if the passage is defined by at least one foraminous wall exposing the molecular sieve bed to air flowing through the passage, gases and odors from the flowing air will be drawn into the pores of the molecular sieve, with far less moisture being adsorbed by the molecular sieve than when the air to be filtered is passed directly through the molecular sieve bed. Since the bulk of the moisture in the air to be filtered flows on through the passage, the working life of the molecular sieve, for the removal of gases and odors, is markedly increased.
While good results are achieved in a static version of the unit wherein the air flows through the passage by the flue effect, for more rapid and efficient gas and odor removal, it is preferred to draw the air through the passage by means of a fan.
The passage may be open, or it may be filled with polyester, fiberglass, or baffle means to slow down or diffuse the air to allow and encourage the small gas and odor molecules to sort of "sling off" toward the openings in the foraminous wall of the passage.
An indicator material may be mixed in the molecular sieve which will change color when the adsorbing property of the molecular sieve has been spent, and the bed needs replacement. Under these circumstances, the container for the bed should be transparent so that the indicator can be viewed.